HH is a genetic disorder characterized by an iron overload due to increased dietary iron absorption. Between 3–4 mg of iron may be absorbed daily with HH, compared to 1–2 mg absorbed usually. As iron absorption increases, the amount of iron bound to transferrin and transported in the plasma subsequently increases.
Regular iron storage sites become overloaded with no available mechanism for excreting excess absorbed iron, producing ferritin levels that far exceed normal. As a result, iron is deposited in the parenchymal cells of the liver, pancreas, pituitary, heart, synovium, and other tissues with high concentrations of transferrin receptors. Iron over regular cellular ferritin stores generates free radicals, and reactive oxygen intermediates that cause cell damage to organs and tissues. This process results in the clinical condition known as iron overload, a hallmark feature of HH.
Altered iron absorption is also found in other diseases, but a comprehensive discussion is beyond the scope of this unit.
